This invention relates to the production of a methylolated hydantoin from a hydantoin and a non-aqueous formaldehyde, e.g., paraformaldehyde. More particularly, this invention relates to the production of a crystallized methylolated hydantoin from hydantoin derivatives and paraformaldehyde under certain conditions in which the reaction diluent used, if any, is the product itself. Using this method, a dry, relatively pure product is obtained without the need for a separation process to remove a reaction medium.
Methylolated hydantoins are colorless, odorless, water-soluble compounds used as formaldehyde donors or cross-linking agents in various industrial systems and commercial products. For example, the textile industry uses 5,5-dimethylhydantoin-formaldehyde adducts to make crease-resistant cotton. In the cosmetic industry, 1,3-dimethylol-5,5-dimethylhydantoin (DMDMH) is used as a preservative. DMDMH has been proven an effective antimicrobial agent that is safe for handlers, users and the environment when used under proper conditions.
Several methods for the production of the condensate product of 5,5-dimethylhydantoin and formaldehyde have been suggested in the past. Japanese Patent No. 4709 (1966) discloses preparing DMDMH in an aqueous solution by mixing one mole of dimethylhydantoin and three to five aqueous moles of formaldehyde (37% by weight), heating the mixture at 80.degree. C. for 25 to 30 minutes, and stirring. No catalyst is needed for the reaction. U.S. Pat. No. 3,987,184 describes a process for the production of an aqueous solution of DMDMH by reacting a ratio of 1.85 to 4.2 moles of formaldehyde per mole of dimethylhydantoin in water. The pH of the solution is adjusted to be within the range of 7 to 9, and the reaction takes place at 22.degree. to 65.degree. C.
As shown by the above-mentioned patents, the methods of producing methylolated hydantoins, particularly DMDMH, have generally involved reactions in an aqueous solution. The resulting product is usually transported as a liquid and used as an aqueous solution. Thus, costs include solvent and the expense of transporting volumes that include not only the DMDMH itself, but also the aqueous solution. If a dry product is desired, a tedious, time-consuming, separation process would be required as an additional production step.
Another disadvantage of the prior methods involving reactions in aqueous medium is that the hydantoin must have sufficient water solubility to effect reaction between the hydantoin and aqueous formaldehyde. Thus, reactions of hydantoins which are substituted with alkyl groups &gt;C.sub.2 at the 5-position cannot readily be carried out.
Accordingly, it is the primary object of the present invention to produce economically a methylolated hydantoin product in essentially 100% active form which can be transported as a solid.
Another object of this invention is to produce a methylolated hydantoin in relatively pure form without the resulting formation of by-products.
A further object of this invention is to produce an effectively dry methylolated hydantoin product without using a separation or drying technique to isolate the final product.
It is yet another object of this invention to produce methylolated hydantoins in relatively pure form that are not readily prepared by prior art techniques.
These and other objects of our invention will be apparent from the discussion which follows.